The objective of this research is to study the biochemical controls involved in the differentiation and development of lung tissue. Hormonal, nutritional and genetic factors will be analysed using isotopic and immunochemical techniques. Since vitamin A is apparently involved in the differentiation of lung and corticoids have been implicated in the process of maturation of this tissue, efforts will be made to characterize the specific binding proteins for retinol, and a separate one for retinoic acid recently discovered in this laboratory and to correlate the appearance of those proteins with the levels of the "corticoid receptors" in the lung during perinatal development. It will be attempted to isolate the retinol and retinoic acid binding protein from rabbtit lungs, and to identify the function of the component in the metabolism of the lung. The properties of lung chromatin and its components (nonhistone proteins) during ontogeny of the lung as well as interaction of the retinol and corticoid binding protein with the components of the lung nucleus will be studied. Using an immunochemical method developed in this laboratory in conjunction with chemical procedures the changes in the structure and function of chromatin will be studied during perinatal development of the lung.